You can solve this question using two different methods. One is obviously a hit and trial method in which you keep guessing a number which gives the same amount of total cost. Second is forming two different equations and then solving them using simultaneous methods learnt.
The correct answer is 75 miles. I used the hit and trial method. You can see 20 + 75 * 0.35 = 46.25 and similarly 35 + 75 * 0.15 = 46.25. Hence the same cost.
